Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a first image of a display screen or portion thereof with a transitional graphical user interface;

FIG. 2 is a front view of a second image thereof;

FIG. 3 is a front view of a third image thereof;

FIG. 4 is a front view of a fourth image thereof;

FIG. 5 is a front view of a fifth image thereof; and,

FIG. 6 is a front view of a sixth image thereof.

The appearance of the transitional graphical user interface sequentially transitions between the images shown in FIGS. 1-6 . The process or period in which one image transitions to another image forms no part of the claimed design.

The broken line showing of the display screen or portion thereof forms no part of the claimed design. The broken lines showing portions of the transitional graphical user interface form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a transitional graphical user interface, as shown and described. 